Graphical Issues (screen flicker) on Specific Games (River Raid) (NTSC)

[mister-devel]

Graphical Issues (screen flicker) on Specific Games (River Raid) (NTSC)

[MikeS11]

Added river raid image (Happens both CRT and DSK version)

[MikeS11]

Did more digging on my real C64 and the issue is mostly apparent on River Raid for MiSTer.

[MikeS11]

Thought a side by side of the same D64 image on a real C64 and the Mister would show the differences better.

Side by side
https://photos.app.goo.gl/kUVDXG1Nabn3jD3A8

Ill try to do some debugging in Quartus this weekend but i'm pretty new and still learning a lot right now. Its been 15 years since my EE days =/

[sorgelig]

FPGA has very little relation to EE :)
EE knowledge sometimes is disadvantage in FPGA as developer tries to use async clocks working good in real circuit but not in FPGA.
Not every "classic" SW developer knows the assembler. So not every FPGA developer has to be good in EE.

[Commodork]

Hey Sorgelig, MikeS11 and I did some comparing through Discord. I have multiple versions of River Raid and they all work perfectly on both the MiSTer and real hardware. MikeS11's images also work flawlessly on real hardware, but exhibit a strange stutter when scrolling on the MiSTer core. I am not an expert in such things, but it reminds me of other games I've seen that were patched from PAL to NTSC and don't scroll or display perfectly. I/we aren't sure what's causing it, but it seems to be something in that specific disk image, and not the game's engine itself. I wish I could offer more.

[MikeS11]

I've tried to do some debugging in Quartus on the VIC-II timing for NTSC to see why the characters are hanging randomly on the 2 images (DSK/CRT) of river raid I have. I cant find a good trigger but it looks seems like there is a very slightly timing issue only with the character refresh.

I've tried to contact the last one to modify the VIC-II source in hopes to get some of their input but I never did get a response.

Hey Sorgelig, MikeS11 and I did some comparing through Discord. I have multiple versions of River Raid and they all work perfectly on both the MiSTer and real hardware. MikeS11's images also work flawlessly on real hardware, but exhibit a strange stutter when scrolling on the MiSTer core. I am not an expert in such things, but it reminds me of other games I've seen that were patched from PAL to NTSC and don't scroll or display perfectly. I/we aren't sure what's causing it, but it seems to be something in that specific disk image, and not the game's engine itself. I wish I could offer more.

@Commodork
This is present on both my DSK and CRT copies of River Raid
RR.zip